This invention relates to emulsions and dispersions of bitumen modified with functionalized block copolymers. More particularly, it relates to such emulsions and dispersions containing acrylic monomer-containing block copolymers or maleic anhydride functionalized block copolymers.
Asphalt is a common material utilized for the preparation of paving and roofing materials and also for coatings such as pipe coatings and tank liners. While the material is suitable in many respects, it inherently is deficient in some physical properties which it would be highly desirable to improve. Diene polymer rubbers such as styrene-butadiene rubber and styrene-rubber block copolymers such as styrene-butadiene-styrene and styrene-isoprene-styrene block copolymers have been used to dramatically improve the thermal and mechanical properties of asphalts.
Bitumen emulsions and dispersions have been known for some time. They are heterogeneous 2-phase systems consisting of 2 immiscible materials, bitumen and water. The bitumen is dispersed throughout the continuous water phase in the form of discreet globules which are held in suspension by an emulsifier. Such bitumen emulsions and dispersions have a wide variety of uses such as in road construction, horticultural and agricultural applications, slip coats for concrete, protective coats for concrete, pipelines and ironwork and also for sealing cracks and grouting.
Bitumen emulsions and dispersions containing the polymers discussed above are known. Such emulsions and dispersions have the advantage that such polymers ordinarily give to the bitumen alone. However, such emulsions and dispersions have the following disadvantages: they are not sufficiently stable, they may coalesce, irreversibly flocculate or settle or cream, the coalesced bitumen phase has poor properties after water drying and they are difficult to prepare at high polymer loading. These disadvantages are most likely caused by the lack of affinity that the nonpolar polymers have for water.
It is also known to make emulsions and dispersions of the polymers discussed above in water with a surfactant and then add the polymer emulsions and dispersions to bitumen to obtain improved properties. Addition of a polymer emulsion or dispersion to bitumen provides a means of mixing polymer and bitumen which does not require special high shear high temperature mixing equipment. It does not put the polymer and bitumen through an unnecessary heating step. However, when this process is used, it is often difficult to prepare polymer emulsions and dispersions which are stable or ones with very small dispersed polymer particles. This is because of the lack of affinity of these block copolymers for water. A small dispersed polymer particle improves mixing of polymer and bitumen.
Therefore, there is a need for bitumen emulsions and dispersions and bitumen compositions containing polymer emulsions and dispersions which contain polymers which have a strong affinity for water. The present invention provides such emulsions and dispersions and compositions.